serum

The clear, yellowish liquid component of blood,
lymph, and other body fluids, which separates
when they are allowed to clot completely. Serum is composed of blood plasma,
from which fibrinogen has been removed
by means of clotting.

Serum therapy involves injecting serum containing antibodies
(globulins), which can destroy particular
pathogens. Occasionally injected serum gives rise to an allergic reaction
known as serum sickness (see below); a second injection of the same serum
may induce anaphylaxis.

Serum sickness

This is a type of hypersensitivity that may develop about 10 days after
injection with an antiserum of animal origin or after taking certain drugs,
such as penicillins. Symptoms may include
an itchy rash, joint pain, fever, and enlarged
lymph nodes. In severe cases, a state
that is similar to shock develops. Symptoms
of serum sickness usually clear up in a few days; antihistamines
may hasten recovery. In severe cases, a corticosteroid
drug may be prescribed.

Serology

The branch of laboratory medicine concerned with the analysis of blood serum.
Applications of serology include the diagnosis of infectious diseases by
the identification of antibodies, the development
of antiserum preparations for passive immunization, and the determination
of blood groups in paternity testing
and forensic investigations.

Seronegative

A term used to described serum that has undergone testing for an infection
and is found to have no antibodies to the infectious organism under investigation.
The term also refers to the absence of an auto-antibody (one that reacts
against the body's own cells) in a specific condition. An example of this
usage is the lack of rheumatoid factor that occurs in seronegative rheumatoid
arthritis.

Seropositive

Descriptive of serum that has been tested and found to contain antibodies
to the infectious organism.